Vibration detector



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To all 'whom it may conceive."

Re it known that li, Hannan T. Kommas, a citizen oit the United States, residing at Brookl in the county of Kings, State oi New norli, have invented certain new and useful improvements in Vibration `lletectors, ci which the following is a full, clear, conoise and exact description..

'lihis invention relates to vibration detectors and more particularly to a detector oi' this character which, while it may be used lor a variety ort purpos, is especially designed for the detection of vibrations propagated through the water, such as are produced by a marine or submarine vesseln lt is desirable that devices oi this character, especially when employed in the de` tection of the presence of submarine vessels, shall with accuracy to very feeble vibratory eects without becoming unduly resonant in response to any vibrations within the useful range ol frequencies.

Since the detecting device is often submerged to varying depths in water, it may be subjected to varying external pressures which become comparatively large in some instances. rlhereioie it is important that the normal sensitiveness of the device be maintained independently of large variations in its depth ot immersion. lt is sometimes desirable to compensate tor the increased external pressures encountered' in case the device is to be submerged at great depths by subjecting the vibration responsive member thereoi to an abnormal internal pressure, causing:r such member to assume an abnormal position so that at the operating depth, it will assume its natural position, insuring the rnost edicient response of the device.

Heretoiore, it has been proposed to employ a device oi this character using a vibration responsive member, the response of which is substantially independent ot varia tions in external pressures. However, such devices are not entirely suitable for operation at the comparatively great depths which are necessary in soine instances and which re uire compensating internal pressures.

t is the object of this invention to provide an improved device of this character capable of being submerged to a comparativelyy great depth in water, the response thereof not bein materially im aired by' substantial variations from such epth.

ln order to attain this object, in accord ance with one feature oi the invention, a device of this character is provided with a vibration responsive member or diaphragm comprising a relatively thick member oi soit energy-absorbing moisture-prooi material integrally united with a thin member of substantially moisture and gasprooi mate rial, which in turn is integrally united with the moisture and gas-proof .casing ci vthe device, thereby maintaining the internal pressures to ywhich the device may m ini tially subjected. More specically, a composite diaphrag is employed which is composed ot a relatively thick layer oi' soit rubber or similar material vulcanized to or otherwise united with a relatively thin layer of metal .or other material substantiallypreventing the didusion oi gases under pres sure therethrough. Such layer of metal is so proportioned that it does not materially ad'eot the character ot the response of the rubber layer and is soldered, welded or otherwise suitabl attached to the enclosin casing` to provi e a water and gas-proc joint.

Another feature oi the invention resides in the provision of an improved sealing an rangement at the entrance to the casing., To accomplish this result, the normally elective Water seal is reinforced by a duplicate seal arranged in tandem therewith se that in case one seal is rendered inedective due to ome abnormal condition encountered during operation, the entrance oi moisture to the interior oi the casing would be eiiec tually prevented by the other seal.

The above-mentioned and other features ci the invention, not speciiically mentioned, will clearly appear from the following specication andthe annexed drawing, the tigure of which shows a sectional view ci device embodying the inventiona Referring to the dra-Wing, an open end ci a casing l is closed by a thin flexible member 2 preferably of metal and soldered, welded or otherwise suitably secured to the casing i so as to rovide an air and moisture-prooi joint. ulcanized or otherwise suitably integrally united with the face of the member 2 is a comparatively thick layer 3 ot' soft rubber or other' suitable energy-absorbing inherentl damping material. A protecting face mem er 4, provided with a plurality of perforations 6, 1s threaded upon the casing los surface is secured to and moves with the4 metal plate 2. A ring 8 of felt or other suitable energy-absorbing insulating material having suitable stiffness is attached to the diaphragm 2 by cement orl other suitable means and member 9 supported solely by the ring 8 carries a carbon-faced back electrode 10. The electrodes 7 and 10, with a quantity of granular carbon interposed therebetween,

are enclosed within the ring 8. The nut 11 threaded on the stem 12 of the back electrode 10 provides a suitable electrical connection between the leading-in wire 13 which may be connected with an associated grounded electrical circuit and the back electrode 10. The casing 1, which may be grounded, is electrically connected with the front electrode 7 through the metal plate 2. The leading-in conductor 13 passes through an exterior metallic bushing 17 threaded into the casing 1, a washer 19, an exterior bushing of soft rubber 15, a restricted opening in the casing wall formed by an annular portion 16, an interior bushing 14 of soft rubber, a washer 20 and an interior metallic bushing 18 threaded into the casing 1. A plug 21 threaded into the casing 1 equipped with a valve of any suitable type, not shown since it is unessential to a clear understanding of the invention, to provide for the pumping of gas or air into the interior of the casing to adjust the internal pressure thereof as desired.

It is evident that the advance of the op posing bushings 17 and 18 will longitudi nally compress the rubber bushings 15 and 14 between the respective washers 19 and 20 and the opposite sides of the annular projection 16 to cause the bushings to clamp the insulated covering of the conductor 13 to provide independent water seals. The depressed portion of theannular washer 5 provides means for clamping the rubber layer 2 and to retain such layer in its proper posi.- tion practically independent of the metal plate 2. Y

After thedetector is assembled, the cap over the valve in the plug 21 may be removed and air or gas may be forced into the interior of the casing until a suliciently high internal pressure is attained to compensate for the high external pressures to be Il encountered in operation. `The composite diaphragm may be forced outwardidue to this increased pressure but the protecting cover 4 will limit the distance to which it ma be forced. The cap is then replaced an the detector is submerged to the predetermined distance at which the diaphragm will reassume its natural position, as shown in the drawing.

The metal late 2 is so proportioned and the rubber p ate 3 is comparatively thick, therefore possessing considerable mass so that the characteristics of the composite diaphragm are substantially those of a rubber diaphra m. Also, the yielding qualities of the rub er diaphragm permit considerable variations in the submerged depth of the detector from the predetermined depth without materially affecting the response thereof to mechanical vibrations.

It has been found by experimentationthat metals diffuse airor gas so very slowly as compared with rubber that the combining of the thin metal plate 2 with the layer lof rubber 3 ,insures that initial pressures will be maintained substantially constant for a considerable period and permits the use of a composite diaphragm possessing the desirable properties of rubber and also the abovementioned properties of metal.

What is claimed is:

1. In a vibration detector, a casing having an aperture in the Wall thereof, a metallic member closin such aperture and welded to the casing wal a layer of rubber vulcanized to the exterior surface of the member, and a current-varying device secured upon the interior surface of the'member.

2. In a vibration detector, a diaphragm comprising a layer of soft rubber, a layer of metal fastened to one side of said layer of rubber, and an annular metal bearing meman aperture in the wall thereof, a layer of metal sealing such aperture, a layer of rubber attached to the external face of the layer of metal, and a current-varying device secured upon the interior surface of the layer of metal.

4. A vibration detector comprising a casing having an aperture in one side thereof, a metallic layer to seal such aperture, a rubber diaphragm attached to the metallic layer, a protector cap for said diaphragm, a current-varying device secured upon the interior surface of the metallic layer, a c'nductor for said current-varying device, and means for sealing said conducto.f in the wall of said casing.

In witness whereof, I hereunto subscribe my name this 17th day of July A. D., 1919.

HERMAN T. KOHLHAAS. 

